Directive antenna system



Feb. 28, 1933. E l BRUCE DIRECTIVE ANTENNA SYSTEM 4 Sheets-Sheet l FiledOct.v 11, 1929 u /r/GZ Vfaaff o/A @NAM Fon' ANTENNA nf F/'.

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ATTH/VEY Feb.2s,1933.; E. BRUCE I 1,899,410

DIRECTIVE ANTENNA SYS TBI Filed Oct. 11, 1929 4 Sheets-Sheet 2 l ASEGMfA/r a z 5 fg a f7 m @f5 gmx/Zwam /wj //sz 0 6.7./ ///w,f

VERT/CAL PLA NE CHARACTE//snc Cum/Es .n By@ TW Feb. `28, 1933. E, BRUCE1,899,410*E DIRECTIVE ANTENNA' sYsTE A T TRNE Y 40 shou Patented Feb. i1933 aflssufn MARN ma? "UN-Irfan; s'rnrras PATENT OFFICE i EDMOND BRUCE,OF BANK, JERSEY, ASSIGNOB TO BELL TELEPHONE LABO- RATONES, INCORPORATED,OF NEW YORK, N. Y., A CORPORATION F NEW YORK nrnnc'rrvn ANTENNA SYSTEMAppia-.mamy mea ,october 11, 1929. semi Nofasaazo.

This invention relates `to aerial systems,

and more particularly to directive antennae for use in such systems.

An Object of theinvention is to render a directive antenna capable ofeffective operation over a considerable range., of wave` lengths.Another object of the invention is to increase the` receivingeffectiveness of an n antenna. An additional object of the invention isto enable an antenna to have a desirably sharp selectivity both in avertical plane and in a horizontal plane. A still further object is thereduction lof fading` in Wave propagation. i

It is well known that the most effective height for a simple verticalantenna with a ground connection at its lower end is onehalf the wavelength of the waves transmitted Thisis because the elemental lengths ofo i such an antenna absorb o emit, as the case may be, energies whichconspire when superposed to yield a resultant that .is greater inmalgnitude than may bev had from a similary excited similar antenna ofshorter or longer length. It has been found,however, that the receivingeil'ectivenesswhich is characteristi'c of a vertical half-wave len hantenna may be retained and in fact en anced by an increase in thelength ofthe antenna accompanied by a definite tilt of the antennatoward' or away from the remote cooperating sending station. The simplegeneral rule is that the length of the tilted antenna should beequivalent to a half-wave length of the transmitted waves plus a lengthequal to the projection of the antenna on a plane parallel to thedirection of the wave propagation. In

the case of horizontally Vpropa ated Waves and rfect ground, the lengtho the antenna ld lbe equal to a half-wave length increased by thehorizontal pro'ection ofthe tiltedffantenna. If the ground is imperfectwill be slightly different from the 8 V9. 1

also that in the case of a tilted antenna several wavelengths long, theeffective response ofthe antenna varies but little )with aconsiderablevchange in wave length of the transmitted waves', assumingthat the Wg'energy of the transmitted'waves and their direction ofpropagation' remain unchanged. It is accordingly feasible to employ suchani antenna in 'a system in which it is desirable or necessary to change`wave lengths froml` time to time and this is an extremely impor- 55tant feature of the invention. It is also practical to combine theantenna with simple mechanical means for quickly changing the antennatilt to the optimum angle simultaneously'with a change in the wavelength since, by this expedient; accommodation to different wave lengthsof received waves may be achieved without changein length of the antennaor substitution of one antenna for another; and to combine the antenna'with65 mechanical means for rotating the vertical plane of the antennato the optimum position for radiating or absorbing energy.

Tilted antennae constructed according to this invention readily lendthemselves to va- 70 rions combinations and to use in arrays. Such anantenna suitably terminated exhibits a back-end effect which isrelatively very small in comparison with its end-on directiveselectivity. 75

Additional features of the invention and ends which it attains will beapparent from a .perusal of the following specification taken inconnection with the accompanying drawelements, Fig. 6 representing avector diagram for such a system;

7 is a double invertedV antenna co`m- 95 prising two single AV-typeantennae;

v Fig. 8 shows the vertical'plane directional characteristic of atiltedsingle-wireantenna and a vertical singleqpire antenna each one wavelength 1ong;

Fig. 9 represents schematically one system for combining an inverted Vantenna section with means for rotating the vertical plane of theantenna to any desired direction;

Fig. 1 0 shows a single inverted V antenna section associated with meansfor changing the angle of tilt of each leg or element of the V section;s

Figs. 11 and 12 represent, respectively, a unidirectional end-on and aunidirectional broadside antenna system each comprising an exciter and areiiector;

Figs. 13, 14 and 15 are curves for systems which employ the inventionand are designed for a particular wave length. The curves in Fig. 13show the relation between'the angle of tilt of a single linear wireantenna and.

the length of the antenna in the cases of maxand minimum horizontaldirectivity; .the curve of\` Fig. 14 furnishes a means of determiningthe horizontal and vertical proj ections of different length antennae,each tilted at the optimum angle for horizontal directivity; and thecurves in Fig.`15 show the gain in decibels realized in using tiltedantenna of the types and lengths indicated as compared to the resultsobtained with the half-wave vertical antenna; and

Fig. 16 illustrates two inverted V-sections positioned in differentplanes and having common terminals.

Referring to Fig. 1, the reference numeral 1 designates a verticalhalf-wavelength antenna which is associated with a radio translationdevice, such as a receiver or transmitter, by means of transformer 2having windings 4 and 5. The lower terminal of the antenna is connectedthrough winding 5 to the ground 3. f

Assuming the direction ofthe incoming wave to be as shown `by the arrow6l the wave imp inges on all elements such as a,b, @,rl and e of thevertical antenna 1 at the same instant and therefore the various inducedvoltages are in phase witheach other and may be assumed to have thedirections indicated in the second column of Fig. 2. The currentproduced by the voltage in segment e and directly propagated to winding5 will require 'a time corresponding to a half cycle to travel fromsegment e to the coil 5. Similarly, the current directly propagated frompoint d willl require a Vtime corresponding to lthree'- eighths of acycle to reach winding 5 and currents directly propagated frompoints c,b

and "a will require a time corresponding to one-fourth, one-eighth andzero cycles, respectively, in arriving at winding 5. Assumingcounter-clockwise rotation as positive or advancing the individualcurrents in winding 5, at the instant under consideration,

are consequently retarded in respectvto their producing voltages by anamount uivalent to the antenna length separating winding 5 from therespective segments. In column three of the table of Fig. 2 this isrepresented by means of small arrows which indicate direction' only, andnot current magnitudes. Summing up the individual vector currentsdirectly propagated, it will be seen from the vdiagram at the bottom ofthe column of the ly determined. The conditions are as indicated incolumn four of the table. Current from the segment e has a reversal ofphase on account of reflection from the open-ended antenna and thereforearrives at windin 5 at a time corresponding effectively to a ull cycleafter it originates and therefore, at any given instant, as measured atwinding 5 it is retarded a full cycle in respect to the voltage e.Reflected current occasioned by voltage d travels an eighth of a cycleto the open end2 iseiectively retarded a half-cycle by reilectlon andthen is retarded, by the halfwave antenna, another "half-c cle beforereaching coil 5. At the instant 1t arrives at windin 5it is thereforeretarded one and one-eig 'th cycles in respect to the voltage in segmentd. The remaining vectors for the re ected currents are determined in asimilar manner and their resultant is also a diameter of the vectorcircle as shown in the table. This last mentioned resultant, it will beobserved, has the same direction as the resultant for thedirectly-propagated cur-l rent and consequently, both resultants for theantenna of Fig. 1 add or cooperate to give amaximum total resultant or,in other words, maximum'horizontal directivity. The vectors are, ofcourse, rotating and the directions shown by the arrows are relativeonly.

In connection with Fig. 1 it should be noted that if the verticalantenna were one wave length in heightinstead of one-half wave length, aminimum or zero total vector resultant would be obtained for wavespropagated in a horizontal plane. A vertical antenna one wave len h inheight is therefore ceiver but for purposes of this description it- 'toreject horizontal 19 tenna tilted at such an an such an` angle 'that theprojection of the 4antenna on a. plane parallelto the direction 5 of theincoming wave, represented by the arrow 9, is fone-half wave lengthvshorter ,than the length of the antenna proper, that is-,onequarterwavelength-long for the antenna. of Fig. 3. As explainedvectoriallybelow an anle, termed herein the optimum angle for tie givenantenna length, possessesv a maximum directional characteristic in thedirection of the wave propogation. The small lettersl f, g, k, z', y',and l represent small antenna segments spaced aneighth wave length along-the antennae. l

Referrin` to the table of Fig. 4, and to the induced vo agecolumnparticularly, it will be seen than the voltages simultaneously 'inducedin the, segments are of relatively different phase-iy and in thisrespect the system diii'ers from that shown in Fig. 1. This results fromthe fact that the part of the wave 15 or 21; of a cyc e retar ed inrespect to that inducing the voltage' in the segment immediately above.The various phase dierences between the induced elemental voltages andtheir resulting currents through the transformer '8 are Obtained in themanner already explained in connection with Fig. 2, the currents, as inFi .1, being always Vretarded `in respect to t eir voltages with the 5exception of the current directly propagated from the lowest segment. Amaximum resultant is obtained :for the directly-propaated current andzero resultant for the reected current as shown at the bottom of thetable of Fig. 4f.

In all lantennae tilted in accordance with this invention, the resultantof the directlypropagated current is a diameter of a vector circle. Theresultant of the reected current varies from zero, in the case ofantennae having aglength equal to an odd 'quarter multiple of a wavelength, to small values when the length is an even multiple of a quarterwave length; and as the even multiple increases the reflection resultantvdecreases. A n antenna tilted as shown in Fig. 3 has a substantiallyunity front to back-end ratio which may be greatly increased, that is,the effects produced by waves propagated in a direction oppositeto thatindicated by arrow 9 may be practically eliminated by properlyterminating the antenna. It has been found, for. examplethat if Ithesingle wire antenna is equal in length to an odd multiple, greater than.one, of a quarter wave length, a .terminating impedance equal substantially tothe antenna surge impedance will produce unidirectivity;and, if the antenna length equals an even multiple, greater .35 thantwo, of a quarter. wave length, a terinducing the volta e in an onesegment-is minating impedance equal to the product of the antenna surgeimpedance and the sine of :the `angle of tilt. of the vantenna from thepathof propa ation will render the system unilateral. he terminations,however, would notI Vaiiect thel refiection phenomena and' would notchange the characteristicillustrated in Fig. 4- lsince,"for single wiretilted antennae` the resultant reflected current is zero as indicatedinthis figure. Stated "differently, if the tilted antenna has a length`equal to an odd multiple of a quarter'wave length, and is terminated inan impedance equal to its surge impedance, the ratio of the front toback end reception or radiation vis inlinity. If it-has a lengthequal toan even multiple of a quarter wave length and is similarly terminated,the -ratio is small but this ratio increases as the length that is, asthe even multiple, increasesv and by changing the terminating impedanceto a value equal to the product of the surge impedance and the sine ofthe angle oftilt, the ratio may be made infinite. f L

Compared to the 'standard half-wave antenna of Fig. 1 the transmissiongain obtained in using the antenna of Fig. 3 results vprimarily fromythe fact that the latter is longer and more directive than the former.The vertical antenna` receives 'horizontally propagated waves equallyfrom all directions whereas the tilted antenna favors'twooppositedirections, the directivity diagram resembling avigure eight. Comparedto a ver-` tical three-quarter, wave length antenna the final resultantfor the `tilted antenna of Fig.l 3 possesses no reflected componentwhereas the resultant for the vertical antenna includes a reiected aswell as a directly-propagated component.

vIn both Fi s. 2 and 4 he directly-propa-` gated and reected currentvectors'for the extreme top selgment are opposite in phase to those'forv't extreme bottom element.

This condition is necessary in all cases for maximum results. yInotherwords, the an-l tenna should be tilted toward or away from theincoming wave in sucha manner that current originating at the topelement will arrive or,passthrough the receiver a'half-cycle later thanthat simultaneously originating in the bottom element. When thiscondition is fulfilled the antenna Vwill be a half-Wave longer than itsprojection on a plane parallel to the direction of the wave propagationand its angle withthe projection willbe the optimum one as heretoforedefined.

In Fig.5 another embodiment of the invention 'is shown comprisingtwo'conductors 10 and 11 each tilted at the optimumangle qS for thedesired waves and joined to each.

other so as to form an inverted V. v For purposes of illustration thelength of each conductor or element has b een made equal to one wavelength. As in Fig. 3, this length is al half-wave length longer than theprojection of the element on a plane parallel to the direction of thepropagation of the desired `waves; The lower terminal of conductor 10 loteristic but it may be made unidirectional by properly connecting theconductor 11 to ground-through an impedance at m. The small letters m tou designate infinitesimal segments locatedalong conductors and 11,

15 the adjacent segments being a quarter-wave length apart. The arrow 15indicates the direction of the incoming Wave.

Referring to Fig. 6 a vector diagram for lthe structure shown. in Fig. 5is shown. The

2o induced or spaced voltages at the elemental segments m, to 'w arerepresented inl the top row of arrows. As shown in this row of arrows,the voltage induced in segment n is one-eighth of a cycle retarded overthatl induced in segment m and similarly the voltages induced in theremaining elemental segments are one-eighth of a cycle behind thatinduced in the segment immediately adjacent at the right. The second rowof arrows from the top vrepresent the effective or wire voltages at thelsame elemental points. The effective (as regards the effect on winding12) voltages present in conductor 10 as, for nrple, in segments g to uare opposite in phase to those induced in conductor 10 and cooperatewith, rather than oppose, the effective voltages in the other of the twoconductors. This is true since, so far as con- `cerns their joint effectin winding 12, the direction of the elemental voltages in conductor 10are reversed with respect to the voltages in conductor 11 by the bend orapex of the antenna.

The manner of determining the phase reevlation between the voltages andboth the directly-propagated and the reflected currents passing throughwinding 12 has been described in connection with Figs. 1 and 2and willbe outlined only briefly here. The di- .53 rectly-propagatcd currentproduced `by volt- 'age' m will arrive-at coil 12 two complete cyclesbehind the elemental voltage m producing it, inasmuch as the antenna istwo wave lengths long. Current resulting from voltage n, travels adistance equal to one and three-fourth wave lengths along conductors 11and 10 and of course passes through winding 12 one and three-quartercycles behind voltage 11.. Similarly,the direction of the other Cfelemental directly-propagated and reflected currents may be determinedbearing in mind that current flowing to the open end is re- -versed onreflection Aand therefore effectively retarded a'half-cycle. Forexample, reflected current traveling from m arrives at windthe table inFig. 6. It should be observed in regard to the reflected current thatthe resultant for each of conductors 10 and 11 for progressivelyincreasing numbers of segments travels 540 or one and one-half timesaround the vector circle and finally assumes the same direction as theresultant for the other conductor. This double resultant is added to thedouble resultant obtained for the directly-propagated current to givethe total resultant shown at the extreme right in Fig. 6. For wavespropagated in a direction opposite to that shown in this figure thedirect and reflected components will be similar but opposite indirection to the reflected and direct'components, respectively, shown inthe figure. The total resultant will, -of course, also be opposite indirection to that shown in the figure. The system of Fig. 5 is thereforebilaterally directive and equally responsive to waves pro agated in bothdirections.

In Fig. 7 a uni irectional receiving system is shown comprising twoinverted V antennae 16 and v17'. Antenna. 16, the' reflector, is spacedone-fourth of a wave length farther away from the wave source and inthesame vertical plane as antenna 17, the exciter. The arrow 18 indicatesthe direction of the. wave propagation. Each tilted conductor or elementhas a len h fw wave lengths long and is positione at the optimum angle 4for horizontal directivity so that the horizontal projection of eachelement is a halfv los wave length shorter than the element length or`'w-- wave lengths. Reference numeral 19 represents a transformerutilized for connidlrectivity is achieved by means of the reflector in amanner which is familiar to those skilled in the art. The voltageinduced in conductor 16 by the desired waves is retarded one-fourth of acycle in respect to that induced in conductor 17. Since the fieldreradiated from conductor 16 is opposite in phase to that of the spacefield immediately v adjacent` and since there is a quarter-wave lengthspacing between the reflector and exciter, energy from the inverted Vantenna 16 induces a voltage in antenna 17 in phase with the voltageinduced in the latter. The resulting currents therefore asa sist eachother and reception inthis direction posite diis a maximum. Waves fromthe op rectlon, however, mduce a voltage 1,11 the re- Hector. 16 whichleads that simultaneously fi 5 induced in the exciter- 17 by a quarte.`cycle. ,Because of the 180 phase change due toreradiation vand thequarter-wave length s acing, the voltage induced inthe exciter 1 byenergyfrom the reflector 16 is .y po- 10 site 1n phase to that thenbeing induce in fthe exciter. Currents induced by energy from thisundesired direction are therefore effectively suppressed. Y

' ln Fig. 8 polar directional characteristic 15 'curves'in theverticalplane which have been mathematically calculated are shown for alinear receiving antenna having `a length equal to one `wave length andconnected to a perfect ground. The dotted line curve 22 2 containingtwoloops represents the characteristic when the antenna-is verticallypositioned and the full line curve 23 when the antenna is'tilted 30 fromthe vertical in a verticalplane which includes the point of propagation.Along the horizontal axis the distance designated one hundred per centrepresents the maximum desired current obtainable theoretically for thissystem.

tical plane the desired current will; be less than the maximum justmentioned. A study of these curves reveals the fact that there ispractically no reoeption in the horizontal direction when this antennais vertical position` whereas whenit is tilted 30 inV the path of theincoming wave, there is a maximum reception of desired waves.Furthermore, the position of the minor lobe for the tilted antennalindicates that this antenna has a very good characteristic for wavespropagated vertically as Well as horizontally. In other words ithas ahigh angle of response and therefore is particularly adapted for anglesrelatively close to the earths surface asitis believed to be.- For thesame reason the absorbed energy lincluding that reflected by theHeaviside layer arrives over comparati'vely few transmission paths withthe result that fading isv materially reduced. YThe antenna representedpossesses a` bidirectional lcharacteristic but as explained heretforeitrmay be made 4unidirectional byeither the use of a reflector or aproper terminating impedance. I

In Fig. 9 an invertedrrV typeI antenna24 such. as heretofore describedis shown arrangedfso that the vertical plane of the anso tenna may'bechanged to any desired direction. The particular arrangement shown inthis ligure is illustrative only, and it should be understoodthat anysuitable scheme for the direction of the vertical plane 55 so as toinclude therein a distant transmit- When the antenna is tilted in any:other verminimizing static if static is more intense atang' orreceivihg sacan mia be utilized in' place of the rotating means shownhere.

The system schematically shown in this gu're comprises a circular track25 located in a horizontal plane and connected through Ainsulators 26and 27 t0 both lower terminals of the inverted V. One terminal isgrounded through one .winding of transformer 28 which is associated witha translation stem such as atransmitter or receiver., he

other terminal is connected through a.A terminating impedance 29toground for the'v purpe of obtaining a unidirectional characteristic. Theplane of the vantenna. may

Vbe rotated about the supporting tower 30lin/ either direction, theantenna conductors being kept in the same plane by means ofsuitwaves ofany given wave length within cer- -tain limits is illustrated.l Thereference number 32 represents a horizontal track suitably supported andalong which theI conductor or element 33 of the inverted V typeanp tenna34 may be moved. The antenna is supported by a pulley 35 which in turnis supported by a pole or tower 36 and connected to a counterweght 37 sothat when the conductor moves from the position shown by the full lineto the position shown by the dotted line the combination of the pulleyand counterwei'ght cooperate to maintainK eachk element of the antenna34 equal in length and the angle of tilt of each element equal to thatof the other. The antenna is connected to ground through transformer 38which is connected to a receiver for receiving waves from the directionshown by the arrow 39- A transmitter could, of course, be used on thissystem in place of the receiver. If each side A of the inverted V isseveral wave lengths long the apex of the V moves through a comparaivelysmall distance as will be evident from the description given below ofthe curve of Fig. 13. The scheme used in Fig. 10 could of course becombined withv that used in Fig. 9 so that an antenna could beconstructed which would be adjustable to different optimum angles and atthe same time capable of being rotated to any desireddirection formaximum directivity. Such a system would be especially suitable for useon boats and aircraft and in places where it is impractical to construct`an antenna such as shown in- Figs. 11- and to be described.

Figs. 11 and 12 illustrate, respectively, an

end-on and a broadside antenna array of .inverted V type antenna unitsof the inven- -flector section is one-quarter of a wave length fartheraway from the distant station than its corresponding exciter section.The exciter is conductive'ly connected through a transformer 42 t0ground and inductively associated with a transmission line 43 to atranslation device. The deilector is grounded through an impedancecomprising coil 44 and condenser 45. The arrow 46 indicates thedirection of the wave. The system .shown in Fig. 11 is particularlysuitable for use where considerations of ground space are not of primaryimportance. It possesses a very sharp unidirectional characteristicwhich may be greatly improved by properly choosing the number of thesections or inverted .V'antennaa In Fig. 12 a broadside antennaarrangement is schematically shown in perspective. It comprises anexciter row 47 of inverted V sections, such as 48, all the apexes ofwhich are in a plane perpendicular to the direction of the wavepropagation, represented by the arrow 49. The sections are spaced fromeach other the proper distance which, for a given number of sections,will produce the sharpest unidirectional characteristic. In the sameplane with each exciter section and one-quarterl of a wave lengthfarther away from the distant station is another inverted V typesection, such as 50. These sections forma row 51 which comprises thereflector. Both the exciter and the reflector may consist of any numberof sections and are not intended to be limited to' the number shown onthe drawing,

The transmission system shown in Fig. 12 is designed so that currentflowing from each of the exciter sections to the winding 52 oftransformer 53 traverses a distance equal to that which is traversed bycurrents flowing from the remaining excitersections. Similarly, in thetransmission system shown associated withl the reflector sections, thecurrent iowing from each reflector section to ground through theterminating impedance comprising coil 54 and condenser 55 traverses adistance equal to that traversed by the current flowing from the otherreflector sections. The transmission system therefore does not aect thephase relation between the currents of the various sections. Winding 56of transformer 53 is connected to a receiver.

The operation of the system shown 1n Figs. 11 and 12issimilartothatofthewell Vknown end-on and broadside arrays, respecplications SerialNo. 173,833, filed March 9,- V1927 and Serial No. 235,464, filedNovember 25, 1927, respectively. In both systems the vector resultantfor each section effective at the transformer possesses the samedirection as the other sections. Both systems may, of course, beemployed for transmitting purposes with the same degree of succes.

Referring to Fig. 13 two curves are shown, one of which serves asa meansof determining the tilt from the vertical in the vertical planeincluding the distant station for different lengths of a linear antennafor the condition of maximum horizontal directivity and the other ofwhich similarly determines the tilt for minimum horizontal directivity.Both curves posse a relatively ilat characteristic for antenna lengthsgreater than five wave lengths. An examination of the curve for maximumhorizontal directivi shows that the angle of tilt for an antenna ve wavelengths long is 64 approximately and one ten wave lengths long is 72approximately.

proximately, it is apparent that an antenna. tive wave lengths long andtilted the mean of the above optimum angles that is, 68, toward theincoming wave would be suitable for use over a -frequenc range in whichthe high frequency is dou le that of the low. These curves thereforevdisclose one of the important features of the invention, namely, that atilted antenna is particularly well adapted for use over a comparativelylarge frequency range. Also, it may be seen from a comparison of the twocurves thatan antenna tilted for maximum horizontal directivity mayeasily be adapted for minimum horizontal directivity because of thesmall difference, for an antenna of given length, between the optimumangles for maximum and minimum directivity.

From the curves in Fig. 14 the horizontal and. vertical projections ofantennae tilted at various optimum angles may easily be determlned. Thecurve also illustrates 1in another wayv the Vfact'that for every antennaabove live wave lengths long there little difference in the .variousoptimum a les and that an antenna several wave lengltlis long and tiltedin accordance with the invention is admirably suited for use for severaldifferent frequencies.

From the curves in Fig. 15 thegain realized in using a single tiltedwire, an inverted V-antenna, and a double inverted V antenna of variouslengths over the standard halfwave vertical antenna maybe determined. Aspointed out before, part of the gain obtained is due totheincreasedlength employed lin the tilted antenna as compared to thevertical half-wave standard and part is due to the fact that the antennaradiation resistance is decreased through the sharper directivity.Curves for the dilferent types of 'arrays illustrated in Figs. 11 and 12have been omitted from the` drawing. It is sullicivent to say thatV sucharrays obviously' posse greater transmission gains than that of thesingle sections whose gain over the standard are shown in Fig. 15.

In Fig. 16, two inverted V-sections 57 and 58 'each constructed inaccordance with the invention, are illustrated, one being `disposed 1n avertical plane and the other in a horizontal plane. The two sectionsarejoinedat the common extremities or terminals 60 and 61'. The length'fw of each legof the al1- tenn is a half wave length longer than theprojection of the leg on the pathof the wave propagation designated bynumeral 59. Extremity 60 is connected to ground'62 thijough aterminating .impedance 63 which, s explained above, is of such value asto render the system unilateral and which, as also explainedabove,.incertain`cases onlyis ual to the surge impedance of the antenna.eglhe other terminal 61 is connected to ground 64 through the primary`winding of transformer 65, the secondary of which 1s associated by-`means of line 66 with a receiver'l not shown on the drawings.

The operation of the system shown in Fig. 16 is apparent in view of theon given bove with respect tothe previously described figures. It shouldbe noted, however, that the antenn 57: and l58 favor differentcomponents .of the same wave. Antenna 57, for example, absorbs a maximumamount of energy from the vertical component 67 of the polarized wave'68and substantially no euery fromthe horizontal component 69. On the otherhand, antenna 58 absorbs a maximum amountk of en from the horizontalcomponent 69 and little, if any, energy from the vertical component 67.`Obviously the two antennae may be used jointly, `as illustrated, orseparately,

While the invention has been described in connection with certainspecific embodiments it is clear that the invention may be suitablyemployed in many other embodiments, andit is not intended to limit theinvention to those illustrated. For example, arrays comprising singletilted conductors such as illustrated in Fig. 3, andother doubleinverted V systems `comprising a plurality of inverted V antennae lyingin different planes with their apexes or extremities superimposed maywell be employed. What is claimed is: j 1. An antenna comprising aconductor positioned atan angle greater than zero degrees and less thanninety degrees to a lane perpendicularly related `to the path ci?propagation of a wave and having a length substantially equal to a,half-wave length of the desired wave plus the projection of the antennaon the path of the propagated wave.

lso

2. A. directive antenna systemcomprising degree that its' projection onthe horizontal is substantially equal to a multipleof one .wave length.

4. A radio antenna comprising a conduc.-

conductor inclined to the vertical to such a.

tor inclined to the vertical to such a degree that its projection on thehorizontal is substantially equivalent 'to one wave length, the antennahaving a linear dimension substan-` tialglyh equalV to a multiple of ahalf wave len y Y5. An antenna'comprising a tilted conductor having alength substantially equal to a half wave length of the desired wavesplus the projection of the antenna in the path of the waves, a receiverconnected to one terminal and a suitable terminating impedance connectedto the other terminal of th 61A directive antenna-for receiving aplurality of desired waves comprising a tilted conductor having a lengthof the order of five toten wave lengths of the longest desired wave andtilted in the plane of wave propagation at an angle of the order of 189to 25 from the path of propagation.

7. A tilted antenna for receiving a plurality of wav having a lengthgreater than substantially five wave lengths of the longest desired waveand tilted in the plane of wave propagation at an angle less than 25from the path of propagation so that the radiant energies of variouswave lengths within a def f sired range which are absorbed by itsterminal segments yield oppositely directed ef.- fects substantiallywhen one of the -energies his superimposedupon the other, and atranslation device associated with the antenna 8. An' antenna comprisingtwo conductors each positioned at an angle greater than zero vdegrees tothe plane of polarization and each Vhaving Va length equal to ahalf-wave length` of the desired waves plus its projection in the pathof the wave propagation, the uppermost terminals of said conductorsbeing joined.

9. A V-shaped antenna section comprising I one conductor tilted towardand another conductor tilted away from the incoming wave, saidAconductors being of equal length and having a common terminal, \saidlength being substantially equal to a halfwave length of` the desiredwave plus the projection of the conductor in the path of Y 1'5 thewaves, and a translation device associated with said section at aconductor terminal thereof. .s l j n 10. An inverted V-shaped antennasection comprising one conductor tilted toward and another conductortilted away from the incoming wave, said conductors being of equallength and joined at the top, said length being substantially equal to ahalf-wave length of the desired wave plus the projection of theconductor in the path of the waves, a receiv'er connected to the lowerterminal of one conductor, and a suitable terminating impedanceconnectedto the lower terminal ofl the other conductor.

11. A directive antenna system comprising a plurality of V-shapedsections lying in the same plane with each other -and with a distantcooperating station, one of the said sections being an odd multiple of aquarter wave length of the desired wave farther away Y comprisingconductors each positioned at an acute angle to the plane ofpolarization of the desired wave and each having a length equal to' aVhalf-wave length' of the desired wave plus its projection on the path ofwave propagation, said sections lying in diil'erent planes and havingcommon terminals.

14. In combination, an inverted V-shaped antennacomprising tiltedconductors each t having a length equal to a half wave length of thedesired wave plus its projection on the path of wave propagation, saidantenna being rotatably supported at its apex, and one terminal of saidantenna being connected to a translation device and the other terminalto a terminating impedance.

15. In combination with one or more inverted V-shaped antenna sectionseach comprising oppositely tilted conductors, the length of each ofwhich is equal to a half wave length of a desired wave plus theconductor projection onk the path of said Wave,

means for changing the plane of the an- :u

tenna section to any desired direction.

16. In combination with an inverted V- shaped antenna, means forchanging the tilt of each conductor thereof an equal amount, the tilt ofeach conductor of the antenna being ad'usted so that the differencebetween its lengt rand its projection on the path cfa desired Waveequals substantially a half `wave length of said wave.

17. In combination, an inverted V-shaped Y antenna the apex of which isadjustably supported and one terminal thereof movable in the Vpath ofthe desired waves, the tilt of each conductor bein adjusted so that thedifference between itslength and its'l projection on the path of adesired wave equals substantially a half wave length of said Waves, atranslation device connected to the other terminal of said antenna. j

18. In combination, a plurality of inverted V-shaped antenna sectionseach comprising two conductors, means for rotatin the vertical plane ofat least one of the sai sections, -means for equally changing the tiltof the conductors to any desired angle, the

tilt of each conductor being adjusted so that the difference between itslength and its projection on the path of -a desired wave equalssubstantially a half wave length of said wave, a receiver connected toone terminal and a suitable impedance to the other terminal of the saidsection.

19. An end-on unidirectional antenna array for receiving waves .from` adistant source comprising an exciter and a reiector lying in the sameplane, said exciter and reflector each comprising a plurality of V-shaped antenna sections colinearly arranged Y and electricallyconnected, said sections comprisin conductors tilted so that the? lengthof eac conductor is e ual to its projectlon on the path of the receivedWaves plus onehalf wave length of said waves, each re' lector sectionbeing positioned' a quarter 4wave length farther away fromsaid'source."

than a corresponding exciter section, a receive'r connected to theexciter, and a suitable terminating impedance'connected -to thereflector.

20. A broadside unidirectional antenna.

array for receiving waves from a distant source comprismg an exc1ter anda reflector,

'said exciter and reflector each comprising a plurality of parallelV-shaped sections having conductors tilted so that the length of eachconductor is equal to its projection on the path of the received waveslus one-half wave length of said waves, eac exciter section bein in thesame plane with a reflector section, t e exciter sections beingpositioned an equal distance from said source and each reflector sectiona quarter Wave length farther away from said source than -itsorresponding exciter section, a receiver associated with the exciter,and a suitable terminating im edance associated with the reflector.

21. n antenna comprising a conductor having a length substantially equalto an odd multiple of a quarter wave length of a given wave, saidantenna being tilted at an angle such that its projection on the path ofsaid wave is equal to the antenna length minus a half wave length, animpedance connected to one terminal of said antenna, said impedancebeing equal to the surge impedance of the antenna. n 22. An antennacomprising a conductor having a length `substantially equal to a mul`tiple of a half wave length of a given wave, said antenna beingvtiltedat an angle such that its projection on the path of said wave is equalto the antenna length minus a half wave length, an impedance connectedto one terminal of said antenna, said impedance being equal to theproduct of the antenna surge impedance andthe sine of said angle. Inwitness whereof, I hereunto subscribe my name this 5th day of October1929.

EDMOND sRUcE.

